use strict;
use LWP::UserAgent;

$ENV{ HTTPS_CA_FILE } = 'cacerts.pem';

my $ua  = LWP::UserAgent->new;
my $req = HTTP::Request->new('GET', 'https://mail.google.com/');
my $res = $ua->request($req);

print $res->header( 'client-ssl-warning' );